Hazardous materials are typically sealed in canisters for long term storage and to prevent such materials from escaping into the environment. The sealing of canisters for long term storage of high level nuclear waste requires equipment that can be remotely operated with little or no intervention by personnel. Such canisters carrying nuclear waste or other hazardous materials are typically remotely closed, welded, and then inspected before being approved for long term storage. Welding and inspection of such canisters is performed in a hot cell to limit exposure of personnel to radioactive radiation. A hot cell may be a room with thick walls and windows where one can work with radioactive materials that are detrimental to humans. The thick wall and window structures of the hot cell prevent harmful radiation from escaping out of the room. Prior to storage of the canisters, any weld defects of the canister (e.g., of a weld joint) must be identified and repaired. If a defect is detected in a weld joint, such defect must be repaired and the weld joint must be re-welded before approval. Removal of such weld defects may have to be carried out either by machining or by grinding processes.
Sealing of canisters for long term storage of high level nuclear waste requires equipment that can be operated remotely with little or no intervention by personnel. The canisters are typically remotely closed, welded, and then inspected before being approved for storage. Welding and inspection usually take place within a hot cell to limit exposure of personnel to hazards.
Machining processes present problems because cutting fluid or other lubricants may have to be used with tools for the machining processes. Usage of liquids inside the hot cell is undesirable as such a step introduces waste into the hotcell, and therefore additional steps may have to be undertaken to dispose the newly introduced waste products. Grinding processes eliminate the need for the cutting fluid. However, current grinding systems are inadequate for use in hot cells due to lack of automation. Further, current grinding systems are not accurate enough for use with specific weld joint designs (e.g., narrow groove weld joint designs) as they tend to remove too much of the weld from a weld joint, and thus may contribute to addition of excessive heat into the re-welded joint. Excessive heat was found to have detrimental effects on mechanical properties of the weld joints.
It would be desirable to have, in some embodiments, grinding apparatuses to repair weld defects in remote hot cells. It would also be desirable to avoid the above-identified problems by providing automated grinding apparatuses, in some embodiments.
It would be desirable to repair a weld defect of a weld joint without causing further damage to the joint while retaining as much of the original geometry of the joint as it is possible to simplify the repairing of the weld joint defect in some embodiments.